JP2018530857A - Heating panel - Google Patents

Abstract

For rapid direct heating, flexible heaters for electrochemical cells, for example in automotive applications, can be attached directly to the battery pouch cell. High voltage operation compatible with electric vehicles is provided by separating the positive temperature coefficient heating material by a longitudinally extending moat that restricts current to flow primarily in the longitudinal direction. Reduce the tendency of spot generation. [Selection] Figure 1

Description

[Cross-reference to related applications]
This application claims the benefit of US Provisional Application No. 62 / 199,581, filed July 31, 2015, which is incorporated herein by reference in its entirety.

  The present invention relates to electric heaters, and more particularly to thick film polymer electric heaters suitable for use at high voltages.

  Electric vehicles and hybrid electric vehicles use batteries to store energy. In this application, the battery may be exposed to a range of storage temperatures, including sub-freezing temperatures. At low temperatures, the power available for many types of batteries, including lithium ion batteries, is greatly reduced and battery efficiency is reduced.

  Co-pending U.S. Patent Application No. 61 / 977,802, filed April 10, 2014, which is assigned to this assignee and incorporated by reference, is comb-shaped. Described is a heater for an electric vehicle battery in the form of a flexible substrate having a "thick film" polymer positive temperature coefficient (PTC) material on a substrate overlying a conductive electrode. . Electrodes can be used to apply a current through a positive temperature coefficient material, thereby providing a flexible heater unit that can be installed near the battery to heat a battery at cold temperatures. .

  Such flexible heaters are typically used at relatively low voltages, eg, less than 100 volts, but in automotive applications compatible with electric vehicle power systems operating at higher voltages, a given amount of power A higher operating voltage may be desirable to reduce the cost and weight of the wiring by reducing the flow rate of current to obtain.

  We have found that standard thick film polymer heater designs exhibit extreme non-uniformities in current distribution when operating at high voltages (eg, 330 volts DC to 1000 volts DC), causing hot spots and premature failure. It was determined that this could pose a potential risk. This non-uniform current flow occurs despite the inherent current regulation characteristics of the PTC material.

  The present invention achieves this high voltage non-uniform current density by forming a set of “moats” in the PTC material that isolate currents that facilitate parallel current flow without converging. Address the problem. In some embodiments, the insulating channels are periodically cross-linked by a floating bus that serves to restore uniform current flow through the isolated portion of the PTC material. The result is a flexible thick film polymer heater with improved temperature uniformity and capable of operating at higher voltages.

  Specifically, in one embodiment, the invention comprises a battery comprising a flexible polymer substrate and a conductive electrode that communicates between a heater terminal and electrode fingers spaced along a longitudinal axis. A heater panel is provided. A positive temperature coefficient material having a higher resistance than the conductive electrode electrically interconnects the electrode fingers and extends between the electrode fingers. The positive temperature coefficient material has a plurality of insulating moats, the plurality of insulating moats block current flow through the positive temperature coefficient material across the moat, and the moat has a longitudinal length through the positive temperature coefficient material. The arrangement and size prioritize current flow along the directional axis over current flow perpendicular to the longitudinal axis through the positive temperature coefficient material.

  Accordingly, a feature of at least one embodiment of the present invention is to provide a high efficiency cell heater for automotive applications, etc. that can use the available high voltage electricity while minimizing the occurrence of hot spots. It is.

  The moat is a gap in a positive temperature coefficient material whose longitudinal length measured along the longitudinal axis is at least 5 times the transverse height of the moat measured perpendicular to the longitudinal axis. It can be.

  Accordingly, a feature of at least one embodiment of the present invention is to flexibly control the current in a preferred direction by means of strategically arranged isolation gaps.

  The moat can extend continuously between side-by-side pairs of electrode fingers.

  Thus, a feature of at least one embodiment of the present invention is to completely isolate the current flow through the positive temperature coefficient material into an independent set of longitudinal channels.

  The moat follows a serpentine path along the longitudinal axis.

  Accordingly, a feature of at least one embodiment of the present invention is to reduce the effects of local transverse variations in the PTC material by changing the current transverse flow path.

  The heater panel can further comprise a floating electrode extending transversely across the positive temperature coefficient material in a transverse range where a portion of the positive temperature coefficient material is separated by the moat.

  Accordingly, a feature of at least one embodiment of the present invention is that by providing a low resistance transverse floating electrode conductor, it is possible to realign and re-equalize current flow transversely without hot spots. It is to be.

  The floating electrode can be bridged to at least one moat.

  Accordingly, a feature of at least one embodiment of the present invention is to provide a simple structure that eliminates hot spot generation upon poor connection between the floating electrode and the PTC material.

  The positive temperature coefficient material can be a conductive ink.

  Accordingly, a feature of at least one embodiment of the present invention is to provide a method for dealing with thick film PTC materials that may exhibit some process variation that is exacerbated by high voltage operation.

  The conductive electrode can be a conductive ink having a lower resistance than the positive temperature coefficient material.

  Accordingly, a feature of at least one embodiment of the present invention is to provide a simple printing process for manufacturing a heater panel.

  Other features and advantages of the invention will be apparent to those skilled in the art from consideration of the following detailed description, claims, and drawings. In the drawings, like reference numerals are used to refer to like features.

FIG. 3 is an exploded perspective view of a pouch cell having an integral heater element attached to a cell wall according to the present invention. 1 is a top view of a simplified prior art flexible membrane heater showing a PTC material overlying a comb-shaped conductive electrode and also showing a cross-section of some of the different layers of the flexible membrane heater. FIG. FIG. 3 is a simplified diagram from an empirically obtained thermographic representation of the PTC material of the flexible membrane heater of FIG. 2 operating at low voltage, showing uniform limited heating between the conductive electrodes. FIG. 4 is a view similar to FIG. 3, showing the operation of the flexible membrane heater of FIG. 2 at 300 volts and the generation of a “M” shaped heating pattern showing current distribution perturbations that can form hot spots. FIG. 3 is a view similar to FIG. 2 of the first embodiment of the present invention, incorporating in the PTC material a non-linear moat that isolates the current in parallel, facilitating a more uniform current flow at high voltages. FIG. 6 is a view similar to FIGS. 2 and 5 illustrating an alternative embodiment in which alternate moats that isolate currents in parallel are used with floating bus bars to promote current uniformity. FIG. 7 is a partial view of an alternative embodiment to FIG. 6 where the PTC material between the floating bus bars remains aligned and not staggered. FIG. 6 is a partial view of an alternative embodiment of FIG. 5 showing an alternative pattern of non-linear moats that isolate currents in parallel. FIG. 7 is a partial view of the alternative embodiment of FIG. 6 illustrating the use of floating bus bars that cross a limited number of moats that isolate current.

  Before embodiments of the present invention are described in detail, it is understood that the present invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. . The invention is capable of other embodiments and of being practiced or carried out in various ways. Similarly, it is understood that the language and terminology used herein is for the purpose of description and should not be considered limiting. The use of “including” and “comprising” and variations thereof is intended to encompass the items listed above and equivalents thereof as well as further items and equivalents thereof.

  Referring now to FIG. 1, a pouch cell 8 suitable for combination into a battery for use in an electric vehicle such as an automobile is generally flat having an upper rectangular pouch wall 11a and a lower rectangular pouch wall 11b. Can have a prismatic form factor. The upper rectangular pouch wall 11a and the lower rectangular pouch wall 11b are typically composed of a flexible insulating polymer sheet that can be heat sealed at the seam periphery 15 to provide a pouch that defines a sealed volume 17. can do.

  The enclosed volume 17 can hold various plates, separators, and electrolytes selected to provide electrochemical accumulation and release power. Specifically, the volume 17 can hold an upper current collector plate 19a, such as a metal foil or other conductor, the upper current collector plate 19a having a plate area that fits within the volume 17 and an upper current collector. For external connection to the electric plate 19a, the upper rectangular pouch wall 11a and the extended tab electrode 21a projecting beyond the joint peripheral portion 15 of the lower rectangular pouch wall 11b are provided. The upper current collector plate 19a is positioned adjacent to the upper rectangular pouch wall 11a.

  A similar lower current collector plate 19b can be positioned adjacent to the lower rectangular pouch wall 11b and similarly protrudes beyond the plate area that fits in the volume 17 and the seam periphery 15 to provide a tab electrode. The tab electrodes 21b may be arranged so as to be shifted from 21a. The tab electrodes are, for example, on both the left and right sides of one edge of the seam peripheral portion 15.

  The upper current collector plate 19a and the lower current collector plate 19b include a negative electrode material 19c adjacent to the upper current collector plate 19a, a positive electrode material 19d adjacent to the lower current collector plate 19b, and a negative The electrode material 19c and the separator 19e between the positive electrode material 19d can be located on both sides of the stack. In general, each pouch cell 10 will hold a single positive electrode material 19d and a negative electrode material 19c.

  The configuration of the pouch cell as described above is assigned to Envia Systems, Inc., and is hereby incorporated by reference. Can be followed.

  1 and 2, prior art thick film polymer heater 10 can provide a flexible substrate 12 that provides a substantially non-conductive polymer sheet. The example substrate 12 may be a 7 mil polyester material.

  A heated region 13 (in this example, a rectangular region) on the wide upper surface of the flexible substrate 12 can be coated with a substantially continuous thick film of positive temperature coefficient (PTC) material 14. The positive temperature coefficient of resistance changes the flow rate of electricity depending on the temperature of the material. At this time, the flow of electricity increases at lower temperatures and decreases at higher temperatures, usually following a substantially non-linear pattern as a function of temperature. This characteristic results in self-regulation of the temperature of the PTC material 14 when a substantially constant voltage source is applied across the PTC material 14.

  In one embodiment, the PTC material 14 can be a conductive polyester material that exhibits an increase in resistance with temperature and provides a temperature-driven current limiting effect. This inherent current limitation of the PTC material 14 is expected to reduce hot spots in the thick film polymer heater 10 by increasing the resistance in regions where the current flow is excessive.

  The heated region 13 of the flexible substrate 12 can be coated with the PTC material 14 by a variety of techniques including, for example, application of conductive ink using screen printing or the like. Positive temperature coefficient (PTC) heaters suitable for the present invention are described in US Pat. Nos. 4,857,711 and 4,931, to Leslie M. Watts, which are hereby incorporated by reference in their entirety. No. 627 is also disclosed.

  The positive electrode array 16a and the negative electrode array 16b, both of which are formed of a conductive material, may be printed using conductive ink on the top surface of the PTC material 14 or otherwise so as to be in electrical communication with the PTC material 14. Can be applied. These electrode arrays 16a and 16b can be connected via a power source 40, for example, via a high voltage DC or pulse width modulation DC of more than 50 volts connected to the electrical system of the automobile.

  The positive electrode array 16a can have fingers 18a extending across the surface of the PTC material 14 in a first direction along the equally spaced parallel axes 20a. These fingers 18 a can be in electrical communication with a bus conductor 22 a that extends generally perpendicular to an axis 20 a along one edge of the PTC material 14.

  The negative electrode array 16b can have fingers 18b extending across the surface of the PTC material 14 in a second direction opposite to the direction of the fingers 18a, alternately engaging the fingers 18a. Also, these fingers 18b can extend along a regular parallel axis 20b which is equally positioned between the axes 20a and parallel to the axis 20a. Finger 18b can be joined to bus conductor 22b extending generally perpendicular to axis 20b at the edge of PTC material 14 opposite bus conductor 22a.

  The bus conductors 22a and 22b can extend to one end of the substrate 12 and can present a connection terminal 24 to which DC power or pulse width modulated power can be applied. When power is applied to terminal 24, current flows generally through PTC material 14 between fingers 18 a and 18 b in the direction of longitudinal current flow axis 23 that is generally perpendicular to axis 20.

  The conductive material of the electrode array 16, fingers 18, and terminals 24 is typically from a polymer base that includes a particulate filler of a conductive material, such as silver, that provides a much lower resistance than a PTC material with an equivalent cross-sectional area. Conductive polymers such as those synthesized can be used.

  An example thick film polymer heater 10 provides, for example, 24 watts of power over an area of approximately 4 inches × 6 inches, ie, about 1 watt per square inch, and a target temperature range of 55 ° C. to 65 ° C. at room temperature. Can bring. The total resistance between the terminals 24 can be about 5K ohms to 10K ohms at ambient temperature.

  Referring now to FIG. 3, when the thick film polymer heater 10 of FIG. 2 operates at a relatively low voltage, eg, 12 volts, a regular rectangular heating region 26 of substantially uniform but elevated temperature. Is formed between the shafts 20a and 20b. This uniform temperature in the heated region 26 reflects a substantially uniform current flow in these regions along the longitudinal current flow axis 23 between the fingers 18.

  The rectangular heating area 26 is separated by a narrow cold zone 29 aligned with the shaft 20 at the location of the finger 18 (shown in FIG. 2). These low temperature zones 29 are caused by the current flowing to the finger 18 avoiding the PTC material 14 because the current flows in the path of lowest resistance.

  Referring now to FIG. 4, when the thick film polymer heater 10 of FIG. 2 operates at a high voltage, eg, 300 volts, adjacent rectangular heating regions (eg, 26a and 26b) merge across the axis 20. In some cases, however, the expected rectangular current distribution is disturbed. This turbulence draws current from the upper ends of the heating regions 26a and 26b, diverts the current to hot spot locations 27 that are hotter than other regions of the heating region 26 below the fingers of the shaft 20, It adversely affects the uniformity of the heat applied.

  Referring now to FIG. 5, in the first embodiment of the present invention, the high voltage thick film polymer heater 10 can be configured by changing the form of the PTC material 14 between the fingers 18. This change (e.g., between fingers 18a and 18b) introduces a current isolation trench 30 into the PTC material 14 through which no current can flow. The isolation trench 30 can be formed, for example, by removing the PTC material 14 and exposing the substrate 12 in the region of the isolation trench 30. The moat 30 can extend continuously or partially along the side adjacent fingers 18. Generally, the moat 30 has a longitudinal length measured along the longitudinal axis 23 that is at least five times the transverse height of the moat 31 measured perpendicular to the longitudinal axis.

  The isolation moat 30 extends generally along the longitudinal current flow axis 23, thereby forcing a local flow direction of current generally along the axis 23. The isolation moat 30 has a number of separate conductive traces 31 of PTC material that are periodically spaced across the PTC material 14 and extend along the axis 23 in a direction perpendicular to the longitudinal current flow axis 23. Can be formed. In this embodiment, the trace 31 of PTC material has a substantially uniform width (perpendicular to the longitudinal current flow axis 23) running in a zigzag (non-linear) path parallel to the axis 23. it can.

  As described above, the isolation moat 30 forces a substantially independent line of current flow along the axis 23, e.g., in a region transverse to the axis 20 between the heating regions 26 shown in FIG. Prevent current from converging. It should be noted that in this embodiment, the number of fingers 18 is significantly reduced without sacrificing heating uniformity, allowing for a reduction in the conductive material of the fingers 18. In other embodiments, the thick film polymer heater 10 can be similar to the thick film polymer heater 10. This embodiment has been found to be able to operate at voltages between 330 volts DC and 1000 volts DC and to provide improved thermal uniformity at voltages within that range.

  Referring now to FIG. 6, in an alternative embodiment, a series of floating bus bars 32 are arranged between each pair of fingers 18a and 18b, parallel to and evenly spaced between these fingers. Can be placed and placed. It is important that the floating bus bars 32 are not electrically connected to the bus conductors 22 or to the fingers 18 or to each other. The floating bus bar 32 generally extends perpendicular to the current flow path and can span between multiple traces 31 of the PTC material 14. These floating bus bars 32 serve to redistribute the current in a transverse direction between the traces 31 of the PTC material 14 across the moat 30 between the traces 31 in a direction perpendicular to the longitudinal current flow axis 23. Fulfill. The material of the floating bus bar 32 is generally the same as the material of the bus conductors 22 and fingers 18 and has a much lower resistance than the PTC material 14. The floating bus bar 32 can be bridged to the moat 31 or can overlay the PTC material 14 so that it essentially conducts current away from the covered PTC material 14.

  In this embodiment, the moats 30 and traces 31 between each of the floating bus bars 32 or between the floating bus bars 32 and the fingers 18 can be staggered in a transverse direction perpendicular to the longitudinal current flow axis 23. Thus, the traces 31 of the PTC material 14 in a given row 36 (each row is between a given set of floating bus bars 32 or between the floating bus bar 32 and the finger 18) The trace 31 is connected only by the floating bus bar 32 or the finger 18 and is not connected by the direct connection of the PTC material 14. In this way, the possibility of hot spots due to direct current flow without being relaxed between the traces 31 of the different rows 36 is greatly reduced by the floating bus bar 32.

  This embodiment has been found to be able to operate at voltages between 330 volts DC and 1000 volts DC and to provide improved thermal uniformity at voltages within that range.

  Referring now to FIG. 7, it is understood that the thick film polymer heater 10 of FIG. 6 can alternatively allow alignment and direct connection of the PTC traces 31 between the rows 36. This deformation relies on the fingers 18 or floating bus bars 32 redistributing the current and avoiding hot spots at the bridge between the traces 31. This can make it possible to provide a good connection between the traces 31, and the lower resistance material of the floating bus bar 32 is ensured, for example, by a suitable contact area.

  Referring now to FIG. 8, the zigzag PTC material 14 of the trace 31 of FIG. 5 includes a variety of other non-linear shapes including a smooth sinusoidal pattern extending parallel to the axis 23. It is understood that can be taken. These wavy patterns are collectively referred to as “serpentine”. These are wavy patterns, but on average proceed along the longitudinal axis 23. The trace 31 can be straight and parallel to the axis 23.

  Referring now to FIG. 9, in an alternative embodiment, the floating bus bar 32 can be divided into pieces along a length perpendicular to the axis 23. Here, each fragment connects only to a limited number of PTC traces 31 in different columns 36 (eg, as shown, one PTC trace 31 in the first column 36 is connected to the second column 36). Only one PTC trace 31 can be connected), further preventing current migration in the direction perpendicular to the longitudinal current flow axis 23.

  These various techniques are similarly spanned by a floating bus bar 32 of the type shown in FIG. 5, for example, evenly spaced between fingers 18a and 18b and parallel to these fingers 18. It can be combined with the trace 31 of FIG.

  In general, resistance refers to bulk resistance or antenna resistance, or both, depending on the context.

  Certain terminology is used herein for reference only and is therefore not intended to be limiting. For example, terms such as “upper”, “lower”, “upper” and “lower” refer to directions in the referenced drawings. Terms such as “front”, “back”, “back”, “bottom” and “lateral” are consistent, but indicate the orientation of a component part in any coordinate system, and its coordinates The system will become apparent by reference to the text and associated drawings describing the components discussed. Such terms may include words specifically mentioned so far, derivatives thereof and words of similar meaning. Similarly, "first", "second", and other such numerical terms referring to a structure do not imply a series or order unless clearly indicated by the context.

  When introducing elements or features of the present disclosure and exemplary embodiments, the articles “a, an”, “the” and “said” are used to refer to such elements or features. It means that one or more of them exist. The terms “comprising”, “including” and “having” are intended to be inclusive and further elements other than those specifically mentioned. Or it means that a feature may exist. The methods, steps, processes, and operations described herein are to be construed as necessarily being performed in the particular order discussed or illustrated, unless specifically specified as the order in which they are performed. Please understand that it is not. It should also be understood that additional or alternative steps may be utilized.

  Various features of the invention are set forth in the appended claims. It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the above form are within the scope of the invention. It is also understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features described or apparent from the text and / or drawings. All of these different combinations constitute various alternative aspects of the invention. The embodiments described herein describe the best mode known for practicing the invention and will enable those skilled in the art to utilize the invention.

  All publications mentioned in this specification, including patent publications and non-patent publications, are hereby incorporated by reference in their entirety.

Claims (14)

A flexible polymer substrate;
A conductive electrode communicating between the heater terminal and electrode fingers spaced apart along the longitudinal axis;
A positive temperature coefficient material having a higher resistance than the conductive electrode, electrically interconnecting the electrode fingers and extending between the electrode fingers, wherein the positive temperature coefficient material is: A plurality of insulating moats, the plurality of insulating moats blocking current flow through the positive temperature coefficient material across the moat, the moat extending in the longitudinal direction through the positive temperature coefficient material Positive temperature coefficient material arranged and sized to prioritize the flow of current along an axis over the flow of current perpendicular to the longitudinal axis through the positive temperature coefficient material When,
A heater panel for a battery.   The moat has a longitudinal length measured along the longitudinal axis that is at least five times the transverse height of the moat measured in a direction perpendicular to the longitudinal axis. The heater panel for a battery according to claim 1, wherein the heater panel is a gap in the temperature coefficient material.   The heater panel for a battery according to claim 1, wherein the moat extends continuously between a side-by-side pair of electrode fingers.   The battery heater panel of claim 2, wherein the positive temperature coefficient material between each electrode finger is separated by a plurality of transversely spaced moats that overlap at each longitudinal position.   The heater panel for a battery according to claim 4, wherein the plurality of transversely spaced moats is at least five moats.   The battery heater panel according to claim 5, wherein the moat follows a serpentine path along the longitudinal axis.   The battery heater of claim 1, further comprising a floating electrode extending transversely across the positive temperature coefficient material in a transverse range in which a portion of the positive temperature coefficient material is separated by a moat. panel.   The battery heater panel according to claim 7, wherein the floating electrode is cross-linked to at least one moat.   An electrochemical device attached to the flexible polymer substrate in thermal communication with the flexible polymer substrate and including at least one flexible positive and negative electrode plate and at least one flexible polymer outer wall. The heater panel for a battery according to claim 1, further comprising a cell.   The battery heater panel of claim 1, further comprising a voltage source in communication with the heater terminal and providing a voltage greater than 50 volts.   The battery heater panel according to claim 1, wherein the positive temperature coefficient material is a conductive ink.   The battery heater panel according to claim 1, wherein the conductive electrode is a conductive ink having a lower resistance than the positive temperature coefficient material.   The heater panel for a battery according to claim 1, wherein the resistance between the terminals is 500 Ω to 10 K ohm at an ambient temperature. A method of heating a battery pack having a plurality of cell pouches,
A flexible polymer substrate;
A conductive electrode communicating between the heater terminal and electrode fingers spaced apart along the longitudinal axis;
A positive temperature coefficient material having a higher resistance than the conductive electrodes, electrically interconnecting the electrode fingers and extending between the electrode fingers, wherein the positive temperature coefficient material comprises a plurality of positive temperature coefficient materials; A plurality of insulating moats, the plurality of insulating moats blocking current flow through the positive temperature coefficient material across the moat, the moat being the longitudinal axis through the positive temperature coefficient material A positive temperature coefficient material that is arranged and sized to prioritize the current flow along the current axis perpendicular to the longitudinal axis through the positive temperature coefficient material. When,
Attaching a heater panel comprising:
Applying a voltage greater than 50 volts to the heater panel to heat each cell pouch;
Including a method.

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